Assistive Grid Power Scheme to Enhance Power Balancing Capacity of Solar Photovoltaic CHB Inverter for Grid-Connected Application

Because of their modular design, cascaded H-bridge multilevel inverters are a good fit for grid-connected photovoltaic systems. Power imbalance occurs in the PV system because of partial shading, aging effect, and damage and dusting of panels, and results in overmodulation of the H-bridge modules. Overmodulation of H-bridge modules increases the distortion in grid current and affects the reliability of the system. Majority of the solutions in literature can handle the power imbalance condition when the required modulation index is not more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{4/\pi}$</tex-math></inline-formula>. However, during the heavy power imbalance condition, the required modulation is more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{4/\pi}$</tex-math></inline-formula>. The popular existing methods to handle heavy power imbalance affect the PV utilization or the system’s power factor. So, to nullify the heavy power imbalance effectively in the cascaded H-bridge inverter fed single-stage single-phase grid-connected PV system, a assistive grid power scheme is presented in this article. The proposed method enhances the power balancing capacity of the PV system by taking necessary power from the grid and injecting this power into the cascaded H-bridge inverter. A circuit for the proposed method is developed in this article and its operation is elaborated. Furthermore, experimental studies along with simulation results are used in this article to validate the suggested methodology.